3 * Bluetooth HCI UART driver
5 * Copyright (C) 2002-2003 Fabrizio Gennari <fabrizio.gennari@philips.com>
6 * Copyright (C) 2004-2005 Marcel Holtmann <marcel@holtmann.org>
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License as published by
11 * the Free Software Foundation; either version 2 of the License, or
12 * (at your option) any later version.
14 * This program is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 * GNU General Public License for more details.
19 * You should have received a copy of the GNU General Public License
20 * along with this program; if not, write to the Free Software
21 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
25 #include <linux/module.h>
27 #include <linux/kernel.h>
28 #include <linux/init.h>
29 #include <linux/types.h>
30 #include <linux/fcntl.h>
31 #include <linux/interrupt.h>
32 #include <linux/ptrace.h>
33 #include <linux/poll.h>
35 #include <linux/slab.h>
36 #include <linux/tty.h>
37 #include <linux/errno.h>
38 #include <linux/string.h>
39 #include <linux/signal.h>
40 #include <linux/ioctl.h>
41 #include <linux/skbuff.h>
42 #include <linux/bitrev.h>
43 #include <asm/unaligned.h>
45 #include <net/bluetooth/bluetooth.h>
46 #include <net/bluetooth/hci_core.h>
50 static bool txcrc
= true;
51 static bool hciextn
= true;
53 #define BCSP_TXWINSIZE 4
55 #define BCSP_ACK_PKT 0x05
56 #define BCSP_LE_PKT 0x06
59 struct sk_buff_head unack
; /* Unack'ed packets queue */
60 struct sk_buff_head rel
; /* Reliable packets queue */
61 struct sk_buff_head unrel
; /* Unreliable packets queue */
63 unsigned long rx_count
;
64 struct sk_buff
*rx_skb
;
65 u8 rxseq_txack
; /* rxseq == txack. */
66 u8 rxack
; /* Last packet sent by us that the peer ack'ed */
67 struct timer_list tbcsp
;
70 BCSP_W4_PKT_DELIMITER
,
84 u8 txack_req
; /* Do we need to send ack's to the peer? */
86 /* Reliable packet sequence number - used to assign seq to each rel pkt. */
90 /* ---- BCSP CRC calculation ---- */
92 /* Table for calculating CRC for polynomial 0x1021, LSB processed first,
93 initial value 0xffff, bits shifted in reverse order. */
95 static const u16 crc_table
[] = {
96 0x0000, 0x1081, 0x2102, 0x3183,
97 0x4204, 0x5285, 0x6306, 0x7387,
98 0x8408, 0x9489, 0xa50a, 0xb58b,
99 0xc60c, 0xd68d, 0xe70e, 0xf78f
102 /* Initialise the crc calculator */
103 #define BCSP_CRC_INIT(x) x = 0xffff
105 /* Update crc with next data byte
107 * Implementation note
108 * The data byte is treated as two nibbles. The crc is generated
109 * in reverse, i.e., bits are fed into the register from the top.
111 static void bcsp_crc_update(u16
*crc
, u8 d
)
115 reg
= (reg
>> 4) ^ crc_table
[(reg
^ d
) & 0x000f];
116 reg
= (reg
>> 4) ^ crc_table
[(reg
^ (d
>> 4)) & 0x000f];
121 /* ---- BCSP core ---- */
123 static void bcsp_slip_msgdelim(struct sk_buff
*skb
)
125 const char pkt_delim
= 0xc0;
127 memcpy(skb_put(skb
, 1), &pkt_delim
, 1);
130 static void bcsp_slip_one_byte(struct sk_buff
*skb
, u8 c
)
132 const char esc_c0
[2] = { 0xdb, 0xdc };
133 const char esc_db
[2] = { 0xdb, 0xdd };
137 memcpy(skb_put(skb
, 2), &esc_c0
, 2);
140 memcpy(skb_put(skb
, 2), &esc_db
, 2);
143 memcpy(skb_put(skb
, 1), &c
, 1);
147 static int bcsp_enqueue(struct hci_uart
*hu
, struct sk_buff
*skb
)
149 struct bcsp_struct
*bcsp
= hu
->priv
;
151 if (skb
->len
> 0xFFF) {
152 BT_ERR("Packet too long");
157 switch (hci_skb_pkt_type(skb
)) {
158 case HCI_ACLDATA_PKT
:
159 case HCI_COMMAND_PKT
:
160 skb_queue_tail(&bcsp
->rel
, skb
);
163 case HCI_SCODATA_PKT
:
164 skb_queue_tail(&bcsp
->unrel
, skb
);
168 BT_ERR("Unknown packet type");
176 static struct sk_buff
*bcsp_prepare_pkt(struct bcsp_struct
*bcsp
, u8
*data
,
177 int len
, int pkt_type
)
179 struct sk_buff
*nskb
;
181 u16
BCSP_CRC_INIT(bcsp_txmsg_crc
);
185 case HCI_ACLDATA_PKT
:
186 chan
= 6; /* BCSP ACL channel */
187 rel
= 1; /* reliable channel */
189 case HCI_COMMAND_PKT
:
190 chan
= 5; /* BCSP cmd/evt channel */
191 rel
= 1; /* reliable channel */
193 case HCI_SCODATA_PKT
:
194 chan
= 7; /* BCSP SCO channel */
195 rel
= 0; /* unreliable channel */
198 chan
= 1; /* BCSP LE channel */
199 rel
= 0; /* unreliable channel */
202 chan
= 0; /* BCSP internal channel */
203 rel
= 0; /* unreliable channel */
206 BT_ERR("Unknown packet type");
210 if (hciextn
&& chan
== 5) {
211 __le16 opcode
= ((struct hci_command_hdr
*)data
)->opcode
;
213 /* Vendor specific commands */
214 if (hci_opcode_ogf(__le16_to_cpu(opcode
)) == 0x3f) {
215 u8 desc
= *(data
+ HCI_COMMAND_HDR_SIZE
);
216 if ((desc
& 0xf0) == 0xc0) {
217 data
+= HCI_COMMAND_HDR_SIZE
+ 1;
218 len
-= HCI_COMMAND_HDR_SIZE
+ 1;
224 /* Max len of packet: (original len +4(bcsp hdr) +2(crc))*2
225 * (because bytes 0xc0 and 0xdb are escaped, worst case is
226 * when the packet is all made of 0xc0 and 0xdb :) )
227 * + 2 (0xc0 delimiters at start and end).
230 nskb
= alloc_skb((len
+ 6) * 2 + 2, GFP_ATOMIC
);
234 hci_skb_pkt_type(nskb
) = pkt_type
;
236 bcsp_slip_msgdelim(nskb
);
238 hdr
[0] = bcsp
->rxseq_txack
<< 3;
240 BT_DBG("We request packet no %u to card", bcsp
->rxseq_txack
);
243 hdr
[0] |= 0x80 + bcsp
->msgq_txseq
;
244 BT_DBG("Sending packet with seqno %u", bcsp
->msgq_txseq
);
245 bcsp
->msgq_txseq
= (bcsp
->msgq_txseq
+ 1) & 0x07;
251 hdr
[1] = ((len
<< 4) & 0xff) | chan
;
253 hdr
[3] = ~(hdr
[0] + hdr
[1] + hdr
[2]);
255 /* Put BCSP header */
256 for (i
= 0; i
< 4; i
++) {
257 bcsp_slip_one_byte(nskb
, hdr
[i
]);
260 bcsp_crc_update(&bcsp_txmsg_crc
, hdr
[i
]);
264 for (i
= 0; i
< len
; i
++) {
265 bcsp_slip_one_byte(nskb
, data
[i
]);
268 bcsp_crc_update(&bcsp_txmsg_crc
, data
[i
]);
273 bcsp_txmsg_crc
= bitrev16(bcsp_txmsg_crc
);
274 bcsp_slip_one_byte(nskb
, (u8
) ((bcsp_txmsg_crc
>> 8) & 0x00ff));
275 bcsp_slip_one_byte(nskb
, (u8
) (bcsp_txmsg_crc
& 0x00ff));
278 bcsp_slip_msgdelim(nskb
);
282 /* This is a rewrite of pkt_avail in ABCSP */
283 static struct sk_buff
*bcsp_dequeue(struct hci_uart
*hu
)
285 struct bcsp_struct
*bcsp
= hu
->priv
;
289 /* First of all, check for unreliable messages in the queue,
290 since they have priority */
292 skb
= skb_dequeue(&bcsp
->unrel
);
294 struct sk_buff
*nskb
;
296 nskb
= bcsp_prepare_pkt(bcsp
, skb
->data
, skb
->len
,
297 hci_skb_pkt_type(skb
));
302 skb_queue_head(&bcsp
->unrel
, skb
);
303 BT_ERR("Could not dequeue pkt because alloc_skb failed");
307 /* Now, try to send a reliable pkt. We can only send a
308 * reliable packet if the number of packets sent but not yet ack'ed
309 * is < than the winsize
312 spin_lock_irqsave_nested(&bcsp
->unack
.lock
, flags
, SINGLE_DEPTH_NESTING
);
314 if (bcsp
->unack
.qlen
< BCSP_TXWINSIZE
) {
315 skb
= skb_dequeue(&bcsp
->rel
);
317 struct sk_buff
*nskb
;
319 nskb
= bcsp_prepare_pkt(bcsp
, skb
->data
, skb
->len
,
320 hci_skb_pkt_type(skb
));
322 __skb_queue_tail(&bcsp
->unack
, skb
);
323 mod_timer(&bcsp
->tbcsp
, jiffies
+ HZ
/ 4);
324 spin_unlock_irqrestore(&bcsp
->unack
.lock
, flags
);
327 skb_queue_head(&bcsp
->rel
, skb
);
328 BT_ERR("Could not dequeue pkt because alloc_skb failed");
333 spin_unlock_irqrestore(&bcsp
->unack
.lock
, flags
);
335 /* We could not send a reliable packet, either because there are
336 * none or because there are too many unack'ed pkts. Did we receive
337 * any packets we have not acknowledged yet ?
340 if (bcsp
->txack_req
) {
341 /* if so, craft an empty ACK pkt and send it on BCSP unreliable
344 struct sk_buff
*nskb
= bcsp_prepare_pkt(bcsp
, NULL
, 0, BCSP_ACK_PKT
);
348 /* We have nothing to send */
352 static int bcsp_flush(struct hci_uart
*hu
)
358 /* Remove ack'ed packets */
359 static void bcsp_pkt_cull(struct bcsp_struct
*bcsp
)
361 struct sk_buff
*skb
, *tmp
;
363 int i
, pkts_to_be_removed
;
366 spin_lock_irqsave(&bcsp
->unack
.lock
, flags
);
368 pkts_to_be_removed
= skb_queue_len(&bcsp
->unack
);
369 seqno
= bcsp
->msgq_txseq
;
371 while (pkts_to_be_removed
) {
372 if (bcsp
->rxack
== seqno
)
374 pkts_to_be_removed
--;
375 seqno
= (seqno
- 1) & 0x07;
378 if (bcsp
->rxack
!= seqno
)
379 BT_ERR("Peer acked invalid packet");
381 BT_DBG("Removing %u pkts out of %u, up to seqno %u",
382 pkts_to_be_removed
, skb_queue_len(&bcsp
->unack
),
386 skb_queue_walk_safe(&bcsp
->unack
, skb
, tmp
) {
387 if (i
>= pkts_to_be_removed
)
391 __skb_unlink(skb
, &bcsp
->unack
);
395 if (skb_queue_empty(&bcsp
->unack
))
396 del_timer(&bcsp
->tbcsp
);
398 spin_unlock_irqrestore(&bcsp
->unack
.lock
, flags
);
400 if (i
!= pkts_to_be_removed
)
401 BT_ERR("Removed only %u out of %u pkts", i
, pkts_to_be_removed
);
404 /* Handle BCSP link-establishment packets. When we
405 * detect a "sync" packet, symptom that the BT module has reset,
406 * we do nothing :) (yet)
408 static void bcsp_handle_le_pkt(struct hci_uart
*hu
)
410 struct bcsp_struct
*bcsp
= hu
->priv
;
411 u8 conf_pkt
[4] = { 0xad, 0xef, 0xac, 0xed };
412 u8 conf_rsp_pkt
[4] = { 0xde, 0xad, 0xd0, 0xd0 };
413 u8 sync_pkt
[4] = { 0xda, 0xdc, 0xed, 0xed };
415 /* spot "conf" pkts and reply with a "conf rsp" pkt */
416 if (bcsp
->rx_skb
->data
[1] >> 4 == 4 && bcsp
->rx_skb
->data
[2] == 0 &&
417 !memcmp(&bcsp
->rx_skb
->data
[4], conf_pkt
, 4)) {
418 struct sk_buff
*nskb
= alloc_skb(4, GFP_ATOMIC
);
420 BT_DBG("Found a LE conf pkt");
423 memcpy(skb_put(nskb
, 4), conf_rsp_pkt
, 4);
424 hci_skb_pkt_type(nskb
) = BCSP_LE_PKT
;
426 skb_queue_head(&bcsp
->unrel
, nskb
);
427 hci_uart_tx_wakeup(hu
);
429 /* Spot "sync" pkts. If we find one...disaster! */
430 else if (bcsp
->rx_skb
->data
[1] >> 4 == 4 && bcsp
->rx_skb
->data
[2] == 0 &&
431 !memcmp(&bcsp
->rx_skb
->data
[4], sync_pkt
, 4)) {
432 BT_ERR("Found a LE sync pkt, card has reset");
436 static inline void bcsp_unslip_one_byte(struct bcsp_struct
*bcsp
, unsigned char byte
)
438 const u8 c0
= 0xc0, db
= 0xdb;
440 switch (bcsp
->rx_esc_state
) {
441 case BCSP_ESCSTATE_NOESC
:
444 bcsp
->rx_esc_state
= BCSP_ESCSTATE_ESC
;
447 memcpy(skb_put(bcsp
->rx_skb
, 1), &byte
, 1);
448 if ((bcsp
->rx_skb
->data
[0] & 0x40) != 0 &&
449 bcsp
->rx_state
!= BCSP_W4_CRC
)
450 bcsp_crc_update(&bcsp
->message_crc
, byte
);
455 case BCSP_ESCSTATE_ESC
:
458 memcpy(skb_put(bcsp
->rx_skb
, 1), &c0
, 1);
459 if ((bcsp
->rx_skb
->data
[0] & 0x40) != 0 &&
460 bcsp
->rx_state
!= BCSP_W4_CRC
)
461 bcsp_crc_update(&bcsp
->message_crc
, 0xc0);
462 bcsp
->rx_esc_state
= BCSP_ESCSTATE_NOESC
;
467 memcpy(skb_put(bcsp
->rx_skb
, 1), &db
, 1);
468 if ((bcsp
->rx_skb
->data
[0] & 0x40) != 0 &&
469 bcsp
->rx_state
!= BCSP_W4_CRC
)
470 bcsp_crc_update(&bcsp
->message_crc
, 0xdb);
471 bcsp
->rx_esc_state
= BCSP_ESCSTATE_NOESC
;
476 BT_ERR("Invalid byte %02x after esc byte", byte
);
477 kfree_skb(bcsp
->rx_skb
);
479 bcsp
->rx_state
= BCSP_W4_PKT_DELIMITER
;
485 static void bcsp_complete_rx_pkt(struct hci_uart
*hu
)
487 struct bcsp_struct
*bcsp
= hu
->priv
;
490 if (bcsp
->rx_skb
->data
[0] & 0x80) { /* reliable pkt */
491 BT_DBG("Received seqno %u from card", bcsp
->rxseq_txack
);
493 bcsp
->rxseq_txack
%= 0x8;
496 /* If needed, transmit an ack pkt */
497 hci_uart_tx_wakeup(hu
);
500 bcsp
->rxack
= (bcsp
->rx_skb
->data
[0] >> 3) & 0x07;
501 BT_DBG("Request for pkt %u from card", bcsp
->rxack
);
504 if ((bcsp
->rx_skb
->data
[1] & 0x0f) == 6 &&
505 bcsp
->rx_skb
->data
[0] & 0x80) {
506 hci_skb_pkt_type(bcsp
->rx_skb
) = HCI_ACLDATA_PKT
;
508 } else if ((bcsp
->rx_skb
->data
[1] & 0x0f) == 5 &&
509 bcsp
->rx_skb
->data
[0] & 0x80) {
510 hci_skb_pkt_type(bcsp
->rx_skb
) = HCI_EVENT_PKT
;
512 } else if ((bcsp
->rx_skb
->data
[1] & 0x0f) == 7) {
513 hci_skb_pkt_type(bcsp
->rx_skb
) = HCI_SCODATA_PKT
;
515 } else if ((bcsp
->rx_skb
->data
[1] & 0x0f) == 1 &&
516 !(bcsp
->rx_skb
->data
[0] & 0x80)) {
517 bcsp_handle_le_pkt(hu
);
523 struct hci_event_hdr hdr
;
524 u8 desc
= (bcsp
->rx_skb
->data
[1] & 0x0f);
526 if (desc
!= 0 && desc
!= 1) {
529 skb_pull(bcsp
->rx_skb
, 4);
530 memcpy(skb_push(bcsp
->rx_skb
, 1), &desc
, 1);
533 hdr
.plen
= bcsp
->rx_skb
->len
;
534 memcpy(skb_push(bcsp
->rx_skb
, HCI_EVENT_HDR_SIZE
), &hdr
, HCI_EVENT_HDR_SIZE
);
535 hci_skb_pkt_type(bcsp
->rx_skb
) = HCI_EVENT_PKT
;
537 hci_recv_frame(hu
->hdev
, bcsp
->rx_skb
);
539 BT_ERR("Packet for unknown channel (%u %s)",
540 bcsp
->rx_skb
->data
[1] & 0x0f,
541 bcsp
->rx_skb
->data
[0] & 0x80 ?
542 "reliable" : "unreliable");
543 kfree_skb(bcsp
->rx_skb
);
546 kfree_skb(bcsp
->rx_skb
);
548 /* Pull out BCSP hdr */
549 skb_pull(bcsp
->rx_skb
, 4);
551 hci_recv_frame(hu
->hdev
, bcsp
->rx_skb
);
554 bcsp
->rx_state
= BCSP_W4_PKT_DELIMITER
;
558 static u16
bscp_get_crc(struct bcsp_struct
*bcsp
)
560 return get_unaligned_be16(&bcsp
->rx_skb
->data
[bcsp
->rx_skb
->len
- 2]);
564 static int bcsp_recv(struct hci_uart
*hu
, const void *data
, int count
)
566 struct bcsp_struct
*bcsp
= hu
->priv
;
567 const unsigned char *ptr
;
569 BT_DBG("hu %p count %d rx_state %d rx_count %ld",
570 hu
, count
, bcsp
->rx_state
, bcsp
->rx_count
);
574 if (bcsp
->rx_count
) {
576 BT_ERR("Short BCSP packet");
577 kfree_skb(bcsp
->rx_skb
);
578 bcsp
->rx_state
= BCSP_W4_PKT_START
;
581 bcsp_unslip_one_byte(bcsp
, *ptr
);
587 switch (bcsp
->rx_state
) {
588 case BCSP_W4_BCSP_HDR
:
589 if ((0xff & (u8
) ~ (bcsp
->rx_skb
->data
[0] + bcsp
->rx_skb
->data
[1] +
590 bcsp
->rx_skb
->data
[2])) != bcsp
->rx_skb
->data
[3]) {
591 BT_ERR("Error in BCSP hdr checksum");
592 kfree_skb(bcsp
->rx_skb
);
593 bcsp
->rx_state
= BCSP_W4_PKT_DELIMITER
;
597 if (bcsp
->rx_skb
->data
[0] & 0x80 /* reliable pkt */
598 && (bcsp
->rx_skb
->data
[0] & 0x07) != bcsp
->rxseq_txack
) {
599 BT_ERR("Out-of-order packet arrived, got %u expected %u",
600 bcsp
->rx_skb
->data
[0] & 0x07, bcsp
->rxseq_txack
);
602 kfree_skb(bcsp
->rx_skb
);
603 bcsp
->rx_state
= BCSP_W4_PKT_DELIMITER
;
607 bcsp
->rx_state
= BCSP_W4_DATA
;
608 bcsp
->rx_count
= (bcsp
->rx_skb
->data
[1] >> 4) +
609 (bcsp
->rx_skb
->data
[2] << 4); /* May be 0 */
613 if (bcsp
->rx_skb
->data
[0] & 0x40) { /* pkt with crc */
614 bcsp
->rx_state
= BCSP_W4_CRC
;
617 bcsp_complete_rx_pkt(hu
);
621 if (bitrev16(bcsp
->message_crc
) != bscp_get_crc(bcsp
)) {
622 BT_ERR("Checksum failed: computed %04x received %04x",
623 bitrev16(bcsp
->message_crc
),
626 kfree_skb(bcsp
->rx_skb
);
627 bcsp
->rx_state
= BCSP_W4_PKT_DELIMITER
;
631 skb_trim(bcsp
->rx_skb
, bcsp
->rx_skb
->len
- 2);
632 bcsp_complete_rx_pkt(hu
);
635 case BCSP_W4_PKT_DELIMITER
:
638 bcsp
->rx_state
= BCSP_W4_PKT_START
;
641 /*BT_ERR("Ignoring byte %02x", *ptr);*/
647 case BCSP_W4_PKT_START
:
654 bcsp
->rx_state
= BCSP_W4_BCSP_HDR
;
656 bcsp
->rx_esc_state
= BCSP_ESCSTATE_NOESC
;
657 BCSP_CRC_INIT(bcsp
->message_crc
);
659 /* Do not increment ptr or decrement count
660 * Allocate packet. Max len of a BCSP pkt=
661 * 0xFFF (payload) +4 (header) +2 (crc)
664 bcsp
->rx_skb
= bt_skb_alloc(0x1005, GFP_ATOMIC
);
666 BT_ERR("Can't allocate mem for new packet");
667 bcsp
->rx_state
= BCSP_W4_PKT_DELIMITER
;
679 /* Arrange to retransmit all messages in the relq. */
680 static void bcsp_timed_event(unsigned long arg
)
682 struct hci_uart
*hu
= (struct hci_uart
*) arg
;
683 struct bcsp_struct
*bcsp
= hu
->priv
;
687 BT_DBG("hu %p retransmitting %u pkts", hu
, bcsp
->unack
.qlen
);
689 spin_lock_irqsave_nested(&bcsp
->unack
.lock
, flags
, SINGLE_DEPTH_NESTING
);
691 while ((skb
= __skb_dequeue_tail(&bcsp
->unack
)) != NULL
) {
692 bcsp
->msgq_txseq
= (bcsp
->msgq_txseq
- 1) & 0x07;
693 skb_queue_head(&bcsp
->rel
, skb
);
696 spin_unlock_irqrestore(&bcsp
->unack
.lock
, flags
);
698 hci_uart_tx_wakeup(hu
);
701 static int bcsp_open(struct hci_uart
*hu
)
703 struct bcsp_struct
*bcsp
;
707 bcsp
= kzalloc(sizeof(*bcsp
), GFP_KERNEL
);
712 skb_queue_head_init(&bcsp
->unack
);
713 skb_queue_head_init(&bcsp
->rel
);
714 skb_queue_head_init(&bcsp
->unrel
);
716 init_timer(&bcsp
->tbcsp
);
717 bcsp
->tbcsp
.function
= bcsp_timed_event
;
718 bcsp
->tbcsp
.data
= (u_long
) hu
;
720 bcsp
->rx_state
= BCSP_W4_PKT_DELIMITER
;
728 static int bcsp_close(struct hci_uart
*hu
)
730 struct bcsp_struct
*bcsp
= hu
->priv
;
732 del_timer_sync(&bcsp
->tbcsp
);
738 skb_queue_purge(&bcsp
->unack
);
739 skb_queue_purge(&bcsp
->rel
);
740 skb_queue_purge(&bcsp
->unrel
);
746 static const struct hci_uart_proto bcsp
= {
751 .enqueue
= bcsp_enqueue
,
752 .dequeue
= bcsp_dequeue
,
757 int __init
bcsp_init(void)
759 return hci_uart_register_proto(&bcsp
);
762 int __exit
bcsp_deinit(void)
764 return hci_uart_unregister_proto(&bcsp
);
767 module_param(txcrc
, bool, 0644);
768 MODULE_PARM_DESC(txcrc
, "Transmit CRC with every BCSP packet");
770 module_param(hciextn
, bool, 0644);
771 MODULE_PARM_DESC(hciextn
, "Convert HCI Extensions into BCSP packets");